A teenager has been cleared of causing a serious head injury to another youth who has spent eight months in a coma.

Barristers in the case and the judge agreed before the start of the trial that the full extent of Carl Randall's injuries should not be revealed to the jury in case it affected their decision.

The Teesside Crown Court jury found Andrew McGinn, 19, of Birkhall Road, Middlesbrough, not guilty of causing grievous bodily harm to Mr Randall on July 29 last year. He had denied the charge.

The prosecution had alleged that Mr Randall's collapse with a blood clot in his skull, six hours after McGinn had punched him, was the result of that punch.

The Crown claimed that McGinn had walked up to Mr Randall at last year's Pallister Park Family Fun Day and hit him "in the cheekbone area" after being told that the other man had been caught breaking into his parents' car.

Home Office pathologist James Sunter, cross examined by McGinn's barrister Philip Lancaster, told the court that the six-hour gap between a blow to the head and the development of such an injury was "typical", it could take up to 12 hours.

He told Mr Lancaster that a blow to the cheekbone, which had not left a mark, could not have produced the injury.

He said the blow would have had to be further round the side of the head. If it was the punch which caused the injury, said the doctor, the eye witnesses must have been mistaken as to where the impact occurred.

Mr Lancaster asked the jury to accept that the injured youth could have been involved in other incidents which could have caused the injury within the 12-hour "window".

Telling the jury they had to be sure beyond doubt to convict, he said: "We just don't know."